A variety of inflatable sport balls, such as a soccer ball, conventionally exhibit a layered structure that includes a casing, a restriction structure, and an inflatable bladder. The casing provides an exterior layer of the sport ball and is generally formed from a plurality of durable, wear-resistant panels joined together along abutting edges. Although panel configurations may vary significantly, the casing of a traditional soccer ball includes thirty-two panels, twelve of which have a pentagonal shape and twenty of which have a hexagonal shape. The restriction structure forms a middle layer of the sport ball and is positioned between the bladder and the casing. In general, the restriction structure is formed from materials with a limited degree of stretch in order to restrict expansion of the bladder, as discussed in greater detail below. The bladder, which has an inflatable configuration, is located within the restriction structure to provide an inner layer of the sport ball. In order to facilitate inflation (i.e., with air), the bladder generally includes a valved opening that extends through each of the restriction structure and casing, thereby being accessible from an exterior of the sport ball.
Inflation of the bladder induces the sport ball to take on a substantially spherical shape. More particularly, fluid pressure from air within the bladder causes the bladder to expand and place an outward force upon the restriction structure. In turn, the restriction structure places an outward force upon the casing. In order to limit expansion of the bladder and also limit tension in the casing, the restriction structure generally has a configuration or is formed from a material with a limited degree of stretch. In other words, the bladder expands within the restriction structure, but the stretch characteristics of the restriction structure effectively prevent the expansion from inducing significant tension in the casing. Accordingly, the restriction structure acts to restrain the expansion of the bladder, while permitting outward forces from the bladder to induce a substantially spherical shape in the casing, thereby imparting a substantially spherical shape to the sport ball.
The restriction structures of conventional sport balls may have a variety of configurations. As an example, a conventional restriction structure may be formed from a thread, yarn, or filament that is repeatedly wound around the bladder in various directions to form a mesh that restrains expansion of the bladder. As another example, a conventional restriction structure may be formed from a plurality of generally flat or planar textile elements that are stitched together to form a structure that extends around the bladder. As yet another example, a conventional restriction structure may be formed from a plurality of generally flat or planar textile strips that are impregnated with latex and placed in an overlapping configuration around the bladder. In some conventional sport balls, the restriction structure may also be bonded, joined, or otherwise incorporated into the casing as a backing material.